It is usual, in band-saws, to place the saw outside the frame and column which support the driving parts, thus exposing the saws to injury from handling lunber about them, also rendering them dangerous to the operator either from breakage of unsound saws, or by the saw sliding off the upper pul- ley while m motion and falling upon the operator, from which accidents have occurred. The main feature in this machine has been to produce a band-saw perfectly safe to the operator, and fully protected from injury to the saw—combining neat ness and utility in all its parts. By reference to the annexed engraving it will be noticed that the saw is placed to run upward inside the column, A, under the top arch, over the upper or tension pulley, and down inside the front frame and behind the guide bar, B, which can be adjusted up and down to the required hight for the work to be done. The saw also runs through a superior adjustable guide above and below the work, and a guide in the column near A, guiding equally well all widths of saws. The upper or tension pulley,is entirely inclosed by the gate, C, which opens to change the saws, and perfectly protects the operator from the saw in case of breakage or sliding off. The upper pulley shaft is held in oscillating.vield-. ing, and adjustable bearings, that can easily be set to accommodate the running of the saw. Manufactured by the inventor, J. T. Plass, at his iron-works, Nos. 202 and 204 East 29th St., New York, where they can he seen in operation. Malleable Cast Iron. For the production of this material, says Van JYostrand's Magazine, most of the German founders use first fusion pig free from sulphur and phosphorus, or Scotch -pig. Styria also furn'sOieg duitablc iron, which can be ased only in the north of Germany, however, on account of the expense of transportation arid high-duties. On account of th*t competition of wrought iron, great cheapness is very essential to its sale. The makers keep secret the brand or grade of iron which they employ, but it is well understood that the brands are not the same in different establishments. The iron is melted in plumbago crucibles, holding about 30 kilogrammes. They are covered with porcelain lids to keep out impurities and cinders, which reduce the high heat requisite for the process. The fire in which the crucibles are placed, is from -630 m. to 940 m. square, and is surrounded with bricks of porcelain earth. The use of blast is not advantageous, since the economy of time is offset by a greater consumption of coke. The natural draft of the chimney is sufficient when the furnace is properly constructed. As we have said, an essential condition of success is a high heat at the moment of pouring. Practice enables the founder to estimate the heat of the furnace, arid he recognizes the precise moment by plunging a bar of red-hot iron into the crucible, from which, upon being withdrawn, the metal flies off in sparks. The crucibles are raised with tongs, with curved jaws, and the pouring is done with all possible promptitude—the surface being first cleaned. By cementation the casting acquires the properties of wrought iron, having some analogy to steel. The operation consists in subjecting the castings to a prolonged red heat, in a bath of pulverized red hematite. They are arranged in boxes of cast iron called muffles. It would seem that the cylindrical form ought to be most advantageous for the boxes, but practically they are simply square, and with covers which should keep out entirely the least access of air. In arranging the castings in the boxes they are placed in fayers alternately with layers of hematite. The cementing lurnace is very simple. The grate is in front, and the draft of the chimney carries the hot air around the boxes. The heat should be conducted with care, starting rather vigorously, in order to reach quickly tho desired temperature; then supplying the furnace at regular intervals. Tho cementation lasts three, four, and five days, according to tho size of the pieces. A charge is about 350 to 450 kilogrammes of castings. In arranging the charges laige pieces should not be mingled with small, and those muffles containing the larger pieces should be placed in the furnace first. On the other hand the smaller objects are placed on the solo of the furnace. Without these precautions many pieces may be burned, or badly decarburized—the latter becoming something intermediate between iron and steel. When the operation is deemed complete, the fire is allowed to fall, but the furnace is not un- charged until it has gradually cooled. Practice plays an important part in the management of the firing, as the temperature can be judged of only after prolonged experience. Next to the fuel, the greatest expense is the cementing boxes, which are often serviceable only for a single operation.
This article was originally published with the title "Plass' Patent Safety Band-Saw"